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Linux/lib/xz/xz_dec_lzma2.c

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  1 /*
  2  * LZMA2 decoder
  3  *
  4  * Authors: Lasse Collin <lasse.collin@tukaani.org>
  5  *          Igor Pavlov <http://7-zip.org/>
  6  *
  7  * This file has been put into the public domain.
  8  * You can do whatever you want with this file.
  9  */
 10 
 11 #include "xz_private.h"
 12 #include "xz_lzma2.h"
 13 
 14 /*
 15  * Range decoder initialization eats the first five bytes of each LZMA chunk.
 16  */
 17 #define RC_INIT_BYTES 5
 18 
 19 /*
 20  * Minimum number of usable input buffer to safely decode one LZMA symbol.
 21  * The worst case is that we decode 22 bits using probabilities and 26
 22  * direct bits. This may decode at maximum of 20 bytes of input. However,
 23  * lzma_main() does an extra normalization before returning, thus we
 24  * need to put 21 here.
 25  */
 26 #define LZMA_IN_REQUIRED 21
 27 
 28 /*
 29  * Dictionary (history buffer)
 30  *
 31  * These are always true:
 32  *    start <= pos <= full <= end
 33  *    pos <= limit <= end
 34  *
 35  * In multi-call mode, also these are true:
 36  *    end == size
 37  *    size <= size_max
 38  *    allocated <= size
 39  *
 40  * Most of these variables are size_t to support single-call mode,
 41  * in which the dictionary variables address the actual output
 42  * buffer directly.
 43  */
 44 struct dictionary {
 45         /* Beginning of the history buffer */
 46         uint8_t *buf;
 47 
 48         /* Old position in buf (before decoding more data) */
 49         size_t start;
 50 
 51         /* Position in buf */
 52         size_t pos;
 53 
 54         /*
 55          * How full dictionary is. This is used to detect corrupt input that
 56          * would read beyond the beginning of the uncompressed stream.
 57          */
 58         size_t full;
 59 
 60         /* Write limit; we don't write to buf[limit] or later bytes. */
 61         size_t limit;
 62 
 63         /*
 64          * End of the dictionary buffer. In multi-call mode, this is
 65          * the same as the dictionary size. In single-call mode, this
 66          * indicates the size of the output buffer.
 67          */
 68         size_t end;
 69 
 70         /*
 71          * Size of the dictionary as specified in Block Header. This is used
 72          * together with "full" to detect corrupt input that would make us
 73          * read beyond the beginning of the uncompressed stream.
 74          */
 75         uint32_t size;
 76 
 77         /*
 78          * Maximum allowed dictionary size in multi-call mode.
 79          * This is ignored in single-call mode.
 80          */
 81         uint32_t size_max;
 82 
 83         /*
 84          * Amount of memory currently allocated for the dictionary.
 85          * This is used only with XZ_DYNALLOC. (With XZ_PREALLOC,
 86          * size_max is always the same as the allocated size.)
 87          */
 88         uint32_t allocated;
 89 
 90         /* Operation mode */
 91         enum xz_mode mode;
 92 };
 93 
 94 /* Range decoder */
 95 struct rc_dec {
 96         uint32_t range;
 97         uint32_t code;
 98 
 99         /*
100          * Number of initializing bytes remaining to be read
101          * by rc_read_init().
102          */
103         uint32_t init_bytes_left;
104 
105         /*
106          * Buffer from which we read our input. It can be either
107          * temp.buf or the caller-provided input buffer.
108          */
109         const uint8_t *in;
110         size_t in_pos;
111         size_t in_limit;
112 };
113 
114 /* Probabilities for a length decoder. */
115 struct lzma_len_dec {
116         /* Probability of match length being at least 10 */
117         uint16_t choice;
118 
119         /* Probability of match length being at least 18 */
120         uint16_t choice2;
121 
122         /* Probabilities for match lengths 2-9 */
123         uint16_t low[POS_STATES_MAX][LEN_LOW_SYMBOLS];
124 
125         /* Probabilities for match lengths 10-17 */
126         uint16_t mid[POS_STATES_MAX][LEN_MID_SYMBOLS];
127 
128         /* Probabilities for match lengths 18-273 */
129         uint16_t high[LEN_HIGH_SYMBOLS];
130 };
131 
132 struct lzma_dec {
133         /* Distances of latest four matches */
134         uint32_t rep0;
135         uint32_t rep1;
136         uint32_t rep2;
137         uint32_t rep3;
138 
139         /* Types of the most recently seen LZMA symbols */
140         enum lzma_state state;
141 
142         /*
143          * Length of a match. This is updated so that dict_repeat can
144          * be called again to finish repeating the whole match.
145          */
146         uint32_t len;
147 
148         /*
149          * LZMA properties or related bit masks (number of literal
150          * context bits, a mask dervied from the number of literal
151          * position bits, and a mask dervied from the number
152          * position bits)
153          */
154         uint32_t lc;
155         uint32_t literal_pos_mask; /* (1 << lp) - 1 */
156         uint32_t pos_mask;         /* (1 << pb) - 1 */
157 
158         /* If 1, it's a match. Otherwise it's a single 8-bit literal. */
159         uint16_t is_match[STATES][POS_STATES_MAX];
160 
161         /* If 1, it's a repeated match. The distance is one of rep0 .. rep3. */
162         uint16_t is_rep[STATES];
163 
164         /*
165          * If 0, distance of a repeated match is rep0.
166          * Otherwise check is_rep1.
167          */
168         uint16_t is_rep0[STATES];
169 
170         /*
171          * If 0, distance of a repeated match is rep1.
172          * Otherwise check is_rep2.
173          */
174         uint16_t is_rep1[STATES];
175 
176         /* If 0, distance of a repeated match is rep2. Otherwise it is rep3. */
177         uint16_t is_rep2[STATES];
178 
179         /*
180          * If 1, the repeated match has length of one byte. Otherwise
181          * the length is decoded from rep_len_decoder.
182          */
183         uint16_t is_rep0_long[STATES][POS_STATES_MAX];
184 
185         /*
186          * Probability tree for the highest two bits of the match
187          * distance. There is a separate probability tree for match
188          * lengths of 2 (i.e. MATCH_LEN_MIN), 3, 4, and [5, 273].
189          */
190         uint16_t dist_slot[DIST_STATES][DIST_SLOTS];
191 
192         /*
193          * Probility trees for additional bits for match distance
194          * when the distance is in the range [4, 127].
195          */
196         uint16_t dist_special[FULL_DISTANCES - DIST_MODEL_END];
197 
198         /*
199          * Probability tree for the lowest four bits of a match
200          * distance that is equal to or greater than 128.
201          */
202         uint16_t dist_align[ALIGN_SIZE];
203 
204         /* Length of a normal match */
205         struct lzma_len_dec match_len_dec;
206 
207         /* Length of a repeated match */
208         struct lzma_len_dec rep_len_dec;
209 
210         /* Probabilities of literals */
211         uint16_t literal[LITERAL_CODERS_MAX][LITERAL_CODER_SIZE];
212 };
213 
214 struct lzma2_dec {
215         /* Position in xz_dec_lzma2_run(). */
216         enum lzma2_seq {
217                 SEQ_CONTROL,
218                 SEQ_UNCOMPRESSED_1,
219                 SEQ_UNCOMPRESSED_2,
220                 SEQ_COMPRESSED_0,
221                 SEQ_COMPRESSED_1,
222                 SEQ_PROPERTIES,
223                 SEQ_LZMA_PREPARE,
224                 SEQ_LZMA_RUN,
225                 SEQ_COPY
226         } sequence;
227 
228         /* Next position after decoding the compressed size of the chunk. */
229         enum lzma2_seq next_sequence;
230 
231         /* Uncompressed size of LZMA chunk (2 MiB at maximum) */
232         uint32_t uncompressed;
233 
234         /*
235          * Compressed size of LZMA chunk or compressed/uncompressed
236          * size of uncompressed chunk (64 KiB at maximum)
237          */
238         uint32_t compressed;
239 
240         /*
241          * True if dictionary reset is needed. This is false before
242          * the first chunk (LZMA or uncompressed).
243          */
244         bool need_dict_reset;
245 
246         /*
247          * True if new LZMA properties are needed. This is false
248          * before the first LZMA chunk.
249          */
250         bool need_props;
251 };
252 
253 struct xz_dec_lzma2 {
254         /*
255          * The order below is important on x86 to reduce code size and
256          * it shouldn't hurt on other platforms. Everything up to and
257          * including lzma.pos_mask are in the first 128 bytes on x86-32,
258          * which allows using smaller instructions to access those
259          * variables. On x86-64, fewer variables fit into the first 128
260          * bytes, but this is still the best order without sacrificing
261          * the readability by splitting the structures.
262          */
263         struct rc_dec rc;
264         struct dictionary dict;
265         struct lzma2_dec lzma2;
266         struct lzma_dec lzma;
267 
268         /*
269          * Temporary buffer which holds small number of input bytes between
270          * decoder calls. See lzma2_lzma() for details.
271          */
272         struct {
273                 uint32_t size;
274                 uint8_t buf[3 * LZMA_IN_REQUIRED];
275         } temp;
276 };
277 
278 /**************
279  * Dictionary *
280  **************/
281 
282 /*
283  * Reset the dictionary state. When in single-call mode, set up the beginning
284  * of the dictionary to point to the actual output buffer.
285  */
286 static void dict_reset(struct dictionary *dict, struct xz_buf *b)
287 {
288         if (DEC_IS_SINGLE(dict->mode)) {
289                 dict->buf = b->out + b->out_pos;
290                 dict->end = b->out_size - b->out_pos;
291         }
292 
293         dict->start = 0;
294         dict->pos = 0;
295         dict->limit = 0;
296         dict->full = 0;
297 }
298 
299 /* Set dictionary write limit */
300 static void dict_limit(struct dictionary *dict, size_t out_max)
301 {
302         if (dict->end - dict->pos <= out_max)
303                 dict->limit = dict->end;
304         else
305                 dict->limit = dict->pos + out_max;
306 }
307 
308 /* Return true if at least one byte can be written into the dictionary. */
309 static inline bool dict_has_space(const struct dictionary *dict)
310 {
311         return dict->pos < dict->limit;
312 }
313 
314 /*
315  * Get a byte from the dictionary at the given distance. The distance is
316  * assumed to valid, or as a special case, zero when the dictionary is
317  * still empty. This special case is needed for single-call decoding to
318  * avoid writing a '\0' to the end of the destination buffer.
319  */
320 static inline uint32_t dict_get(const struct dictionary *dict, uint32_t dist)
321 {
322         size_t offset = dict->pos - dist - 1;
323 
324         if (dist >= dict->pos)
325                 offset += dict->end;
326 
327         return dict->full > 0 ? dict->buf[offset] : 0;
328 }
329 
330 /*
331  * Put one byte into the dictionary. It is assumed that there is space for it.
332  */
333 static inline void dict_put(struct dictionary *dict, uint8_t byte)
334 {
335         dict->buf[dict->pos++] = byte;
336 
337         if (dict->full < dict->pos)
338                 dict->full = dict->pos;
339 }
340 
341 /*
342  * Repeat given number of bytes from the given distance. If the distance is
343  * invalid, false is returned. On success, true is returned and *len is
344  * updated to indicate how many bytes were left to be repeated.
345  */
346 static bool dict_repeat(struct dictionary *dict, uint32_t *len, uint32_t dist)
347 {
348         size_t back;
349         uint32_t left;
350 
351         if (dist >= dict->full || dist >= dict->size)
352                 return false;
353 
354         left = min_t(size_t, dict->limit - dict->pos, *len);
355         *len -= left;
356 
357         back = dict->pos - dist - 1;
358         if (dist >= dict->pos)
359                 back += dict->end;
360 
361         do {
362                 dict->buf[dict->pos++] = dict->buf[back++];
363                 if (back == dict->end)
364                         back = 0;
365         } while (--left > 0);
366 
367         if (dict->full < dict->pos)
368                 dict->full = dict->pos;
369 
370         return true;
371 }
372 
373 /* Copy uncompressed data as is from input to dictionary and output buffers. */
374 static void dict_uncompressed(struct dictionary *dict, struct xz_buf *b,
375                               uint32_t *left)
376 {
377         size_t copy_size;
378 
379         while (*left > 0 && b->in_pos < b->in_size
380                         && b->out_pos < b->out_size) {
381                 copy_size = min(b->in_size - b->in_pos,
382                                 b->out_size - b->out_pos);
383                 if (copy_size > dict->end - dict->pos)
384                         copy_size = dict->end - dict->pos;
385                 if (copy_size > *left)
386                         copy_size = *left;
387 
388                 *left -= copy_size;
389 
390                 memcpy(dict->buf + dict->pos, b->in + b->in_pos, copy_size);
391                 dict->pos += copy_size;
392 
393                 if (dict->full < dict->pos)
394                         dict->full = dict->pos;
395 
396                 if (DEC_IS_MULTI(dict->mode)) {
397                         if (dict->pos == dict->end)
398                                 dict->pos = 0;
399 
400                         memcpy(b->out + b->out_pos, b->in + b->in_pos,
401                                         copy_size);
402                 }
403 
404                 dict->start = dict->pos;
405 
406                 b->out_pos += copy_size;
407                 b->in_pos += copy_size;
408         }
409 }
410 
411 /*
412  * Flush pending data from dictionary to b->out. It is assumed that there is
413  * enough space in b->out. This is guaranteed because caller uses dict_limit()
414  * before decoding data into the dictionary.
415  */
416 static uint32_t dict_flush(struct dictionary *dict, struct xz_buf *b)
417 {
418         size_t copy_size = dict->pos - dict->start;
419 
420         if (DEC_IS_MULTI(dict->mode)) {
421                 if (dict->pos == dict->end)
422                         dict->pos = 0;
423 
424                 memcpy(b->out + b->out_pos, dict->buf + dict->start,
425                                 copy_size);
426         }
427 
428         dict->start = dict->pos;
429         b->out_pos += copy_size;
430         return copy_size;
431 }
432 
433 /*****************
434  * Range decoder *
435  *****************/
436 
437 /* Reset the range decoder. */
438 static void rc_reset(struct rc_dec *rc)
439 {
440         rc->range = (uint32_t)-1;
441         rc->code = 0;
442         rc->init_bytes_left = RC_INIT_BYTES;
443 }
444 
445 /*
446  * Read the first five initial bytes into rc->code if they haven't been
447  * read already. (Yes, the first byte gets completely ignored.)
448  */
449 static bool rc_read_init(struct rc_dec *rc, struct xz_buf *b)
450 {
451         while (rc->init_bytes_left > 0) {
452                 if (b->in_pos == b->in_size)
453                         return false;
454 
455                 rc->code = (rc->code << 8) + b->in[b->in_pos++];
456                 --rc->init_bytes_left;
457         }
458 
459         return true;
460 }
461 
462 /* Return true if there may not be enough input for the next decoding loop. */
463 static inline bool rc_limit_exceeded(const struct rc_dec *rc)
464 {
465         return rc->in_pos > rc->in_limit;
466 }
467 
468 /*
469  * Return true if it is possible (from point of view of range decoder) that
470  * we have reached the end of the LZMA chunk.
471  */
472 static inline bool rc_is_finished(const struct rc_dec *rc)
473 {
474         return rc->code == 0;
475 }
476 
477 /* Read the next input byte if needed. */
478 static __always_inline void rc_normalize(struct rc_dec *rc)
479 {
480         if (rc->range < RC_TOP_VALUE) {
481                 rc->range <<= RC_SHIFT_BITS;
482                 rc->code = (rc->code << RC_SHIFT_BITS) + rc->in[rc->in_pos++];
483         }
484 }
485 
486 /*
487  * Decode one bit. In some versions, this function has been splitted in three
488  * functions so that the compiler is supposed to be able to more easily avoid
489  * an extra branch. In this particular version of the LZMA decoder, this
490  * doesn't seem to be a good idea (tested with GCC 3.3.6, 3.4.6, and 4.3.3
491  * on x86). Using a non-splitted version results in nicer looking code too.
492  *
493  * NOTE: This must return an int. Do not make it return a bool or the speed
494  * of the code generated by GCC 3.x decreases 10-15 %. (GCC 4.3 doesn't care,
495  * and it generates 10-20 % faster code than GCC 3.x from this file anyway.)
496  */
497 static __always_inline int rc_bit(struct rc_dec *rc, uint16_t *prob)
498 {
499         uint32_t bound;
500         int bit;
501 
502         rc_normalize(rc);
503         bound = (rc->range >> RC_BIT_MODEL_TOTAL_BITS) * *prob;
504         if (rc->code < bound) {
505                 rc->range = bound;
506                 *prob += (RC_BIT_MODEL_TOTAL - *prob) >> RC_MOVE_BITS;
507                 bit = 0;
508         } else {
509                 rc->range -= bound;
510                 rc->code -= bound;
511                 *prob -= *prob >> RC_MOVE_BITS;
512                 bit = 1;
513         }
514 
515         return bit;
516 }
517 
518 /* Decode a bittree starting from the most significant bit. */
519 static __always_inline uint32_t rc_bittree(struct rc_dec *rc,
520                                            uint16_t *probs, uint32_t limit)
521 {
522         uint32_t symbol = 1;
523 
524         do {
525                 if (rc_bit(rc, &probs[symbol]))
526                         symbol = (symbol << 1) + 1;
527                 else
528                         symbol <<= 1;
529         } while (symbol < limit);
530 
531         return symbol;
532 }
533 
534 /* Decode a bittree starting from the least significant bit. */
535 static __always_inline void rc_bittree_reverse(struct rc_dec *rc,
536                                                uint16_t *probs,
537                                                uint32_t *dest, uint32_t limit)
538 {
539         uint32_t symbol = 1;
540         uint32_t i = 0;
541 
542         do {
543                 if (rc_bit(rc, &probs[symbol])) {
544                         symbol = (symbol << 1) + 1;
545                         *dest += 1 << i;
546                 } else {
547                         symbol <<= 1;
548                 }
549         } while (++i < limit);
550 }
551 
552 /* Decode direct bits (fixed fifty-fifty probability) */
553 static inline void rc_direct(struct rc_dec *rc, uint32_t *dest, uint32_t limit)
554 {
555         uint32_t mask;
556 
557         do {
558                 rc_normalize(rc);
559                 rc->range >>= 1;
560                 rc->code -= rc->range;
561                 mask = (uint32_t)0 - (rc->code >> 31);
562                 rc->code += rc->range & mask;
563                 *dest = (*dest << 1) + (mask + 1);
564         } while (--limit > 0);
565 }
566 
567 /********
568  * LZMA *
569  ********/
570 
571 /* Get pointer to literal coder probability array. */
572 static uint16_t *lzma_literal_probs(struct xz_dec_lzma2 *s)
573 {
574         uint32_t prev_byte = dict_get(&s->dict, 0);
575         uint32_t low = prev_byte >> (8 - s->lzma.lc);
576         uint32_t high = (s->dict.pos & s->lzma.literal_pos_mask) << s->lzma.lc;
577         return s->lzma.literal[low + high];
578 }
579 
580 /* Decode a literal (one 8-bit byte) */
581 static void lzma_literal(struct xz_dec_lzma2 *s)
582 {
583         uint16_t *probs;
584         uint32_t symbol;
585         uint32_t match_byte;
586         uint32_t match_bit;
587         uint32_t offset;
588         uint32_t i;
589 
590         probs = lzma_literal_probs(s);
591 
592         if (lzma_state_is_literal(s->lzma.state)) {
593                 symbol = rc_bittree(&s->rc, probs, 0x100);
594         } else {
595                 symbol = 1;
596                 match_byte = dict_get(&s->dict, s->lzma.rep0) << 1;
597                 offset = 0x100;
598 
599                 do {
600                         match_bit = match_byte & offset;
601                         match_byte <<= 1;
602                         i = offset + match_bit + symbol;
603 
604                         if (rc_bit(&s->rc, &probs[i])) {
605                                 symbol = (symbol << 1) + 1;
606                                 offset &= match_bit;
607                         } else {
608                                 symbol <<= 1;
609                                 offset &= ~match_bit;
610                         }
611                 } while (symbol < 0x100);
612         }
613 
614         dict_put(&s->dict, (uint8_t)symbol);
615         lzma_state_literal(&s->lzma.state);
616 }
617 
618 /* Decode the length of the match into s->lzma.len. */
619 static void lzma_len(struct xz_dec_lzma2 *s, struct lzma_len_dec *l,
620                      uint32_t pos_state)
621 {
622         uint16_t *probs;
623         uint32_t limit;
624 
625         if (!rc_bit(&s->rc, &l->choice)) {
626                 probs = l->low[pos_state];
627                 limit = LEN_LOW_SYMBOLS;
628                 s->lzma.len = MATCH_LEN_MIN;
629         } else {
630                 if (!rc_bit(&s->rc, &l->choice2)) {
631                         probs = l->mid[pos_state];
632                         limit = LEN_MID_SYMBOLS;
633                         s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS;
634                 } else {
635                         probs = l->high;
636                         limit = LEN_HIGH_SYMBOLS;
637                         s->lzma.len = MATCH_LEN_MIN + LEN_LOW_SYMBOLS
638                                         + LEN_MID_SYMBOLS;
639                 }
640         }
641 
642         s->lzma.len += rc_bittree(&s->rc, probs, limit) - limit;
643 }
644 
645 /* Decode a match. The distance will be stored in s->lzma.rep0. */
646 static void lzma_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
647 {
648         uint16_t *probs;
649         uint32_t dist_slot;
650         uint32_t limit;
651 
652         lzma_state_match(&s->lzma.state);
653 
654         s->lzma.rep3 = s->lzma.rep2;
655         s->lzma.rep2 = s->lzma.rep1;
656         s->lzma.rep1 = s->lzma.rep0;
657 
658         lzma_len(s, &s->lzma.match_len_dec, pos_state);
659 
660         probs = s->lzma.dist_slot[lzma_get_dist_state(s->lzma.len)];
661         dist_slot = rc_bittree(&s->rc, probs, DIST_SLOTS) - DIST_SLOTS;
662 
663         if (dist_slot < DIST_MODEL_START) {
664                 s->lzma.rep0 = dist_slot;
665         } else {
666                 limit = (dist_slot >> 1) - 1;
667                 s->lzma.rep0 = 2 + (dist_slot & 1);
668 
669                 if (dist_slot < DIST_MODEL_END) {
670                         s->lzma.rep0 <<= limit;
671                         probs = s->lzma.dist_special + s->lzma.rep0
672                                         - dist_slot - 1;
673                         rc_bittree_reverse(&s->rc, probs,
674                                         &s->lzma.rep0, limit);
675                 } else {
676                         rc_direct(&s->rc, &s->lzma.rep0, limit - ALIGN_BITS);
677                         s->lzma.rep0 <<= ALIGN_BITS;
678                         rc_bittree_reverse(&s->rc, s->lzma.dist_align,
679                                         &s->lzma.rep0, ALIGN_BITS);
680                 }
681         }
682 }
683 
684 /*
685  * Decode a repeated match. The distance is one of the four most recently
686  * seen matches. The distance will be stored in s->lzma.rep0.
687  */
688 static void lzma_rep_match(struct xz_dec_lzma2 *s, uint32_t pos_state)
689 {
690         uint32_t tmp;
691 
692         if (!rc_bit(&s->rc, &s->lzma.is_rep0[s->lzma.state])) {
693                 if (!rc_bit(&s->rc, &s->lzma.is_rep0_long[
694                                 s->lzma.state][pos_state])) {
695                         lzma_state_short_rep(&s->lzma.state);
696                         s->lzma.len = 1;
697                         return;
698                 }
699         } else {
700                 if (!rc_bit(&s->rc, &s->lzma.is_rep1[s->lzma.state])) {
701                         tmp = s->lzma.rep1;
702                 } else {
703                         if (!rc_bit(&s->rc, &s->lzma.is_rep2[s->lzma.state])) {
704                                 tmp = s->lzma.rep2;
705                         } else {
706                                 tmp = s->lzma.rep3;
707                                 s->lzma.rep3 = s->lzma.rep2;
708                         }
709 
710                         s->lzma.rep2 = s->lzma.rep1;
711                 }
712 
713                 s->lzma.rep1 = s->lzma.rep0;
714                 s->lzma.rep0 = tmp;
715         }
716 
717         lzma_state_long_rep(&s->lzma.state);
718         lzma_len(s, &s->lzma.rep_len_dec, pos_state);
719 }
720 
721 /* LZMA decoder core */
722 static bool lzma_main(struct xz_dec_lzma2 *s)
723 {
724         uint32_t pos_state;
725 
726         /*
727          * If the dictionary was reached during the previous call, try to
728          * finish the possibly pending repeat in the dictionary.
729          */
730         if (dict_has_space(&s->dict) && s->lzma.len > 0)
731                 dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0);
732 
733         /*
734          * Decode more LZMA symbols. One iteration may consume up to
735          * LZMA_IN_REQUIRED - 1 bytes.
736          */
737         while (dict_has_space(&s->dict) && !rc_limit_exceeded(&s->rc)) {
738                 pos_state = s->dict.pos & s->lzma.pos_mask;
739 
740                 if (!rc_bit(&s->rc, &s->lzma.is_match[
741                                 s->lzma.state][pos_state])) {
742                         lzma_literal(s);
743                 } else {
744                         if (rc_bit(&s->rc, &s->lzma.is_rep[s->lzma.state]))
745                                 lzma_rep_match(s, pos_state);
746                         else
747                                 lzma_match(s, pos_state);
748 
749                         if (!dict_repeat(&s->dict, &s->lzma.len, s->lzma.rep0))
750                                 return false;
751                 }
752         }
753 
754         /*
755          * Having the range decoder always normalized when we are outside
756          * this function makes it easier to correctly handle end of the chunk.
757          */
758         rc_normalize(&s->rc);
759 
760         return true;
761 }
762 
763 /*
764  * Reset the LZMA decoder and range decoder state. Dictionary is nore reset
765  * here, because LZMA state may be reset without resetting the dictionary.
766  */
767 static void lzma_reset(struct xz_dec_lzma2 *s)
768 {
769         uint16_t *probs;
770         size_t i;
771 
772         s->lzma.state = STATE_LIT_LIT;
773         s->lzma.rep0 = 0;
774         s->lzma.rep1 = 0;
775         s->lzma.rep2 = 0;
776         s->lzma.rep3 = 0;
777 
778         /*
779          * All probabilities are initialized to the same value. This hack
780          * makes the code smaller by avoiding a separate loop for each
781          * probability array.
782          *
783          * This could be optimized so that only that part of literal
784          * probabilities that are actually required. In the common case
785          * we would write 12 KiB less.
786          */
787         probs = s->lzma.is_match[0];
788         for (i = 0; i < PROBS_TOTAL; ++i)
789                 probs[i] = RC_BIT_MODEL_TOTAL / 2;
790 
791         rc_reset(&s->rc);
792 }
793 
794 /*
795  * Decode and validate LZMA properties (lc/lp/pb) and calculate the bit masks
796  * from the decoded lp and pb values. On success, the LZMA decoder state is
797  * reset and true is returned.
798  */
799 static bool lzma_props(struct xz_dec_lzma2 *s, uint8_t props)
800 {
801         if (props > (4 * 5 + 4) * 9 + 8)
802                 return false;
803 
804         s->lzma.pos_mask = 0;
805         while (props >= 9 * 5) {
806                 props -= 9 * 5;
807                 ++s->lzma.pos_mask;
808         }
809 
810         s->lzma.pos_mask = (1 << s->lzma.pos_mask) - 1;
811 
812         s->lzma.literal_pos_mask = 0;
813         while (props >= 9) {
814                 props -= 9;
815                 ++s->lzma.literal_pos_mask;
816         }
817 
818         s->lzma.lc = props;
819 
820         if (s->lzma.lc + s->lzma.literal_pos_mask > 4)
821                 return false;
822 
823         s->lzma.literal_pos_mask = (1 << s->lzma.literal_pos_mask) - 1;
824 
825         lzma_reset(s);
826 
827         return true;
828 }
829 
830 /*********
831  * LZMA2 *
832  *********/
833 
834 /*
835  * The LZMA decoder assumes that if the input limit (s->rc.in_limit) hasn't
836  * been exceeded, it is safe to read up to LZMA_IN_REQUIRED bytes. This
837  * wrapper function takes care of making the LZMA decoder's assumption safe.
838  *
839  * As long as there is plenty of input left to be decoded in the current LZMA
840  * chunk, we decode directly from the caller-supplied input buffer until
841  * there's LZMA_IN_REQUIRED bytes left. Those remaining bytes are copied into
842  * s->temp.buf, which (hopefully) gets filled on the next call to this
843  * function. We decode a few bytes from the temporary buffer so that we can
844  * continue decoding from the caller-supplied input buffer again.
845  */
846 static bool lzma2_lzma(struct xz_dec_lzma2 *s, struct xz_buf *b)
847 {
848         size_t in_avail;
849         uint32_t tmp;
850 
851         in_avail = b->in_size - b->in_pos;
852         if (s->temp.size > 0 || s->lzma2.compressed == 0) {
853                 tmp = 2 * LZMA_IN_REQUIRED - s->temp.size;
854                 if (tmp > s->lzma2.compressed - s->temp.size)
855                         tmp = s->lzma2.compressed - s->temp.size;
856                 if (tmp > in_avail)
857                         tmp = in_avail;
858 
859                 memcpy(s->temp.buf + s->temp.size, b->in + b->in_pos, tmp);
860 
861                 if (s->temp.size + tmp == s->lzma2.compressed) {
862                         memzero(s->temp.buf + s->temp.size + tmp,
863                                         sizeof(s->temp.buf)
864                                                 - s->temp.size - tmp);
865                         s->rc.in_limit = s->temp.size + tmp;
866                 } else if (s->temp.size + tmp < LZMA_IN_REQUIRED) {
867                         s->temp.size += tmp;
868                         b->in_pos += tmp;
869                         return true;
870                 } else {
871                         s->rc.in_limit = s->temp.size + tmp - LZMA_IN_REQUIRED;
872                 }
873 
874                 s->rc.in = s->temp.buf;
875                 s->rc.in_pos = 0;
876 
877                 if (!lzma_main(s) || s->rc.in_pos > s->temp.size + tmp)
878                         return false;
879 
880                 s->lzma2.compressed -= s->rc.in_pos;
881 
882                 if (s->rc.in_pos < s->temp.size) {
883                         s->temp.size -= s->rc.in_pos;
884                         memmove(s->temp.buf, s->temp.buf + s->rc.in_pos,
885                                         s->temp.size);
886                         return true;
887                 }
888 
889                 b->in_pos += s->rc.in_pos - s->temp.size;
890                 s->temp.size = 0;
891         }
892 
893         in_avail = b->in_size - b->in_pos;
894         if (in_avail >= LZMA_IN_REQUIRED) {
895                 s->rc.in = b->in;
896                 s->rc.in_pos = b->in_pos;
897 
898                 if (in_avail >= s->lzma2.compressed + LZMA_IN_REQUIRED)
899                         s->rc.in_limit = b->in_pos + s->lzma2.compressed;
900                 else
901                         s->rc.in_limit = b->in_size - LZMA_IN_REQUIRED;
902 
903                 if (!lzma_main(s))
904                         return false;
905 
906                 in_avail = s->rc.in_pos - b->in_pos;
907                 if (in_avail > s->lzma2.compressed)
908                         return false;
909 
910                 s->lzma2.compressed -= in_avail;
911                 b->in_pos = s->rc.in_pos;
912         }
913 
914         in_avail = b->in_size - b->in_pos;
915         if (in_avail < LZMA_IN_REQUIRED) {
916                 if (in_avail > s->lzma2.compressed)
917                         in_avail = s->lzma2.compressed;
918 
919                 memcpy(s->temp.buf, b->in + b->in_pos, in_avail);
920                 s->temp.size = in_avail;
921                 b->in_pos += in_avail;
922         }
923 
924         return true;
925 }
926 
927 /*
928  * Take care of the LZMA2 control layer, and forward the job of actual LZMA
929  * decoding or copying of uncompressed chunks to other functions.
930  */
931 XZ_EXTERN enum xz_ret xz_dec_lzma2_run(struct xz_dec_lzma2 *s,
932                                        struct xz_buf *b)
933 {
934         uint32_t tmp;
935 
936         while (b->in_pos < b->in_size || s->lzma2.sequence == SEQ_LZMA_RUN) {
937                 switch (s->lzma2.sequence) {
938                 case SEQ_CONTROL:
939                         /*
940                          * LZMA2 control byte
941                          *
942                          * Exact values:
943                          *   0x00   End marker
944                          *   0x01   Dictionary reset followed by
945                          *          an uncompressed chunk
946                          *   0x02   Uncompressed chunk (no dictionary reset)
947                          *
948                          * Highest three bits (s->control & 0xE0):
949                          *   0xE0   Dictionary reset, new properties and state
950                          *          reset, followed by LZMA compressed chunk
951                          *   0xC0   New properties and state reset, followed
952                          *          by LZMA compressed chunk (no dictionary
953                          *          reset)
954                          *   0xA0   State reset using old properties,
955                          *          followed by LZMA compressed chunk (no
956                          *          dictionary reset)
957                          *   0x80   LZMA chunk (no dictionary or state reset)
958                          *
959                          * For LZMA compressed chunks, the lowest five bits
960                          * (s->control & 1F) are the highest bits of the
961                          * uncompressed size (bits 16-20).
962                          *
963                          * A new LZMA2 stream must begin with a dictionary
964                          * reset. The first LZMA chunk must set new
965                          * properties and reset the LZMA state.
966                          *
967                          * Values that don't match anything described above
968                          * are invalid and we return XZ_DATA_ERROR.
969                          */
970                         tmp = b->in[b->in_pos++];
971 
972                         if (tmp == 0x00)
973                                 return XZ_STREAM_END;
974 
975                         if (tmp >= 0xE0 || tmp == 0x01) {
976                                 s->lzma2.need_props = true;
977                                 s->lzma2.need_dict_reset = false;
978                                 dict_reset(&s->dict, b);
979                         } else if (s->lzma2.need_dict_reset) {
980                                 return XZ_DATA_ERROR;
981                         }
982 
983                         if (tmp >= 0x80) {
984                                 s->lzma2.uncompressed = (tmp & 0x1F) << 16;
985                                 s->lzma2.sequence = SEQ_UNCOMPRESSED_1;
986 
987                                 if (tmp >= 0xC0) {
988                                         /*
989                                          * When there are new properties,
990                                          * state reset is done at
991                                          * SEQ_PROPERTIES.
992                                          */
993                                         s->lzma2.need_props = false;
994                                         s->lzma2.next_sequence
995                                                         = SEQ_PROPERTIES;
996 
997                                 } else if (s->lzma2.need_props) {
998                                         return XZ_DATA_ERROR;
999 
1000                                 } else {
1001                                         s->lzma2.next_sequence
1002                                                         = SEQ_LZMA_PREPARE;
1003                                         if (tmp >= 0xA0)
1004                                                 lzma_reset(s);
1005                                 }
1006                         } else {
1007                                 if (tmp > 0x02)
1008                                         return XZ_DATA_ERROR;
1009 
1010                                 s->lzma2.sequence = SEQ_COMPRESSED_0;
1011                                 s->lzma2.next_sequence = SEQ_COPY;
1012                         }
1013 
1014                         break;
1015 
1016                 case SEQ_UNCOMPRESSED_1:
1017                         s->lzma2.uncompressed
1018                                         += (uint32_t)b->in[b->in_pos++] << 8;
1019                         s->lzma2.sequence = SEQ_UNCOMPRESSED_2;
1020                         break;
1021 
1022                 case SEQ_UNCOMPRESSED_2:
1023                         s->lzma2.uncompressed
1024                                         += (uint32_t)b->in[b->in_pos++] + 1;
1025                         s->lzma2.sequence = SEQ_COMPRESSED_0;
1026                         break;
1027 
1028                 case SEQ_COMPRESSED_0:
1029                         s->lzma2.compressed
1030                                         = (uint32_t)b->in[b->in_pos++] << 8;
1031                         s->lzma2.sequence = SEQ_COMPRESSED_1;
1032                         break;
1033 
1034                 case SEQ_COMPRESSED_1:
1035                         s->lzma2.compressed
1036                                         += (uint32_t)b->in[b->in_pos++] + 1;
1037                         s->lzma2.sequence = s->lzma2.next_sequence;
1038                         break;
1039 
1040                 case SEQ_PROPERTIES:
1041                         if (!lzma_props(s, b->in[b->in_pos++]))
1042                                 return XZ_DATA_ERROR;
1043 
1044                         s->lzma2.sequence = SEQ_LZMA_PREPARE;
1045 
1046                 /* Fall through */
1047 
1048                 case SEQ_LZMA_PREPARE:
1049                         if (s->lzma2.compressed < RC_INIT_BYTES)
1050                                 return XZ_DATA_ERROR;
1051 
1052                         if (!rc_read_init(&s->rc, b))
1053                                 return XZ_OK;
1054 
1055                         s->lzma2.compressed -= RC_INIT_BYTES;
1056                         s->lzma2.sequence = SEQ_LZMA_RUN;
1057 
1058                 /* Fall through */
1059 
1060                 case SEQ_LZMA_RUN:
1061                         /*
1062                          * Set dictionary limit to indicate how much we want
1063                          * to be encoded at maximum. Decode new data into the
1064                          * dictionary. Flush the new data from dictionary to
1065                          * b->out. Check if we finished decoding this chunk.
1066                          * In case the dictionary got full but we didn't fill
1067                          * the output buffer yet, we may run this loop
1068                          * multiple times without changing s->lzma2.sequence.
1069                          */
1070                         dict_limit(&s->dict, min_t(size_t,
1071                                         b->out_size - b->out_pos,
1072                                         s->lzma2.uncompressed));
1073                         if (!lzma2_lzma(s, b))
1074                                 return XZ_DATA_ERROR;
1075 
1076                         s->lzma2.uncompressed -= dict_flush(&s->dict, b);
1077 
1078                         if (s->lzma2.uncompressed == 0) {
1079                                 if (s->lzma2.compressed > 0 || s->lzma.len > 0
1080                                                 || !rc_is_finished(&s->rc))
1081                                         return XZ_DATA_ERROR;
1082 
1083                                 rc_reset(&s->rc);
1084                                 s->lzma2.sequence = SEQ_CONTROL;
1085 
1086                         } else if (b->out_pos == b->out_size
1087                                         || (b->in_pos == b->in_size
1088                                                 && s->temp.size
1089                                                 < s->lzma2.compressed)) {
1090                                 return XZ_OK;
1091                         }
1092 
1093                         break;
1094 
1095                 case SEQ_COPY:
1096                         dict_uncompressed(&s->dict, b, &s->lzma2.compressed);
1097                         if (s->lzma2.compressed > 0)
1098                                 return XZ_OK;
1099 
1100                         s->lzma2.sequence = SEQ_CONTROL;
1101                         break;
1102                 }
1103         }
1104 
1105         return XZ_OK;
1106 }
1107 
1108 XZ_EXTERN struct xz_dec_lzma2 *xz_dec_lzma2_create(enum xz_mode mode,
1109                                                    uint32_t dict_max)
1110 {
1111         struct xz_dec_lzma2 *s = kmalloc(sizeof(*s), GFP_KERNEL);
1112         if (s == NULL)
1113                 return NULL;
1114 
1115         s->dict.mode = mode;
1116         s->dict.size_max = dict_max;
1117 
1118         if (DEC_IS_PREALLOC(mode)) {
1119                 s->dict.buf = vmalloc(dict_max);
1120                 if (s->dict.buf == NULL) {
1121                         kfree(s);
1122                         return NULL;
1123                 }
1124         } else if (DEC_IS_DYNALLOC(mode)) {
1125                 s->dict.buf = NULL;
1126                 s->dict.allocated = 0;
1127         }
1128 
1129         return s;
1130 }
1131 
1132 XZ_EXTERN enum xz_ret xz_dec_lzma2_reset(struct xz_dec_lzma2 *s, uint8_t props)
1133 {
1134         /* This limits dictionary size to 3 GiB to keep parsing simpler. */
1135         if (props > 39)
1136                 return XZ_OPTIONS_ERROR;
1137 
1138         s->dict.size = 2 + (props & 1);
1139         s->dict.size <<= (props >> 1) + 11;
1140 
1141         if (DEC_IS_MULTI(s->dict.mode)) {
1142                 if (s->dict.size > s->dict.size_max)
1143                         return XZ_MEMLIMIT_ERROR;
1144 
1145                 s->dict.end = s->dict.size;
1146 
1147                 if (DEC_IS_DYNALLOC(s->dict.mode)) {
1148                         if (s->dict.allocated < s->dict.size) {
1149                                 vfree(s->dict.buf);
1150                                 s->dict.buf = vmalloc(s->dict.size);
1151                                 if (s->dict.buf == NULL) {
1152                                         s->dict.allocated = 0;
1153                                         return XZ_MEM_ERROR;
1154                                 }
1155                         }
1156                 }
1157         }
1158 
1159         s->lzma.len = 0;
1160 
1161         s->lzma2.sequence = SEQ_CONTROL;
1162         s->lzma2.need_dict_reset = true;
1163 
1164         s->temp.size = 0;
1165 
1166         return XZ_OK;
1167 }
1168 
1169 XZ_EXTERN void xz_dec_lzma2_end(struct xz_dec_lzma2 *s)
1170 {
1171         if (DEC_IS_MULTI(s->dict.mode))
1172                 vfree(s->dict.buf);
1173 
1174         kfree(s);
1175 }
1176 

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